Floating-Point IP Cores User Guide

ID 683750
Date 10/27/2021

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3.5.1. ALTFP_ADD_SUM Design Example: Understanding the Simulation Results

The simulation waveform in this design example is not shown in its entirety. Run the design example files in the ModelSim* - Intel® FPGA Edition software to see the complete simulation waveforms.
Figure 15. ALTFP_ADD_SUB Simulation Waveform

This design example implements a floating-point adder for the addition of double-precision format numbers. All the optional input ports (clk_en and aclr) and optional output ports (overflow, underflow, zero, and nan) are enabled.

In this example, the output latency of the multiplier is set to 7 clock cycles. Every addition result appears at the result[] port 7 clock cycles after the input values are captured on the dataa[] and datab[] ports.

The following lists the inputs and corresponding outputs obtained from the simulation waveform.

Table 15.  Summary of Input Values and Corresponding Outputs
Time Event
0 ns, start-up dataa[] value: 0000 0000 0000 0000h

datab[] value: 7FF0 0000 0000 0000h

Output value: All values seen on the output port before the 7th clock cycle are merely due to the behavior of the system during startup and should be disregarded.

4250 ns Output value: 7FF0 0000 0000 0000h

Exception handling ports: overflow asserts

The addition of zero at the input port dataa[], and infinity value at the input port datab[] results in infinity value.

40,511 ns dataa[] value: 0000 0000 0000 0000h

datab[] value: 0000 0000 1000 0123h

The is the addition of a zero and a denormal value.

43,750 ns Output value: 0000 0000 0000 0000h

Exception handling ports: zero remains asserted.

Denormal inputs are not supported and are forced to zero before addition takes place.This results in a zero.